Cross-field electric discharge devices



Feb. 6, 1962 M. WEINSTEIN 3,020,445

CROSS-FIELD ELECTRIC DISCHARGE DEVICES Filed Nov. 24, 1958 2Sheets-Sheet 1 1 i L INVENTORI MYRON WEINSTEIN HIS ATTORNEY.

Fgb. 6, 1962 M. WEINSTEIN 3,020,445

CROSS-FIELD ELECTRIC DISCHARGE DEVICES Filed Nov. 24, 1958 2Sheets-Sheet 2 WATTS FREQUENCY "c INVENTOR MYRON WEINSTEIN,

awful HIS ATTORNEY.

Sates Unite My invention relates to improved cross-field electricdischarge devices and more particularly to such devices includingimproved means for increasing the operating efficiency and power outputthereof and for better adapting the devices for increased stability ofperformance.

In U.S. Patent No. 2,930,933 issued on March 29, 1960, on co-pendingU.S. application Serial No. 723,926, Voltage Tunable Magnetron, filed byG. J. Griffin, Jr. et al. on March 25, 1958, and assigned to the sameassignee as the present invention, is described and claimed across-field device of the voltage tunable magnetron type and comprisingan anode circuit including a plurality of segments supported in acylindrical array in mutually spaced sideby-side relation and havingcoaxially extending therein a non-emissive electrode or cold cathode.The anode circuit and cold cathode define an annular interaction regionand displaced longitudinally therefrom in electrically and physicallyspaced relation to the cold cathode is an emitter. A control electrodesurrounds the emitter and is shaped to provide an axial component ofelectric field to assist in directing electrons from the regionsurrounding the emitter into the interaction region. The controlelectrode, by determining the amount of electrons entering theinteraction region, is effective for determining the power level atwhich the voltage tunable operation takes place. In the just-describedstructure the cold cathode is substantially coextensive with the anode,or, in other words, extends for substantially the full axial length ofthe anode, and is provided at the end opposite the emitter with acylindrical boss-like end cap serving to block electrons tending tomigrate from the corresponding end of the interaction region. This typeof device is adapted for operating in a magnetic field extendingcoaxially through the device and transverse electric fields establishedbetween electrodes and, hence, the designation cross-field device inreference thereto. Additionally, this type of device is generally highlydesirable in that it is capable of operation over a wide frequencyrange, can be effectively easily cut-off, can be operated over asubstantial range of control electrode voltages and can be manufacturedconsistently from tube to tube to assure substantially uniform operationof tubes manufactured in production quantities.

Accordingly, an important object of my invention is to provide a new andimproved cross-field electric discharge device capable of substantiallyincreased operating efiiciency, power output and stability ofperformance while affording also all of the above-described desirablecapabilities of prior devices.

Another object of my invention is to provide a new and improvedcross-field device including a new and improved electrode arrangementfor determining the manner in which electrons from the emitter areeffectively introduced into the interaction region.

Another object of my invention is to provide a new and improvedcross-field device including a new and improved electrode arrangementadapted for efiecting a more rapid introduction of electrons from alongitudinally displaced emitter into the interaction region thereof.

Another object of my invention is to provide a new and improvedcross-field device including a new and improved electrode arrangementfor affording a smooth transition in the average velocity of electronsintroduced from the emitter into the interaction region.

Another object of my invention is to provide a new and "ice improvedcross-field device including a new and improved electrode arrangementeffective for increasing the energy potential of the electronsintroduced into the interaction region of the device, thereby toincrease operating efliciency.

Another object of my invention is to provide a new and improvedcross-field device including new and improved means for virtuallyincreasing the effective length of the interaction region withoutphysically increasing the lengths of the elements defining that region.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of noveltywhichcharacterize my invention will be pointed out with particularity inthe claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a cross-fieldelectrode arrangement including an anode circuit comprising a pluralityof elongated conductive segments arrayed in mutually spaced,side-by-side relation. An emitter and control electrode therefor aredisposed in spaced relation to the ends of the anode segments. Anonemissive electrode extends in laterally spaced relation to the anodeand includes an active surface which extends only partially the lengthof the segments for defining therewith an interaction region which issubstantially spaced from the emitter. Additionally, I provide thenon-emissive electrode with a surface portion inclined toward the planeof the anode on the side of the anode opposite the emitter.

For a better understanding of my invention reference may be had to theaccompanying drawing wherein:

FIGURE 1 is an enlarged elevational view of a section of a magnetrondevice incorporating my invention;

FIGURE 1A illustrates a modified form of the structure shown in FIGURE1;

FIGURE 2 is a schematic illustration of the configuratino of theelectric fields afforded by my improved electrode arrangement;

FIGURE 3 is a family of curves illustrating the power capabilities of adevice incorporating the shortened inter-.

action region of my invention compared with the power capabilities of aprior art device incorporating a longer interaction region; and

FIGURE 4 is a somewhat schematic illustration ofpa modified form of myinvention.

Referring now to the drawing, there is shown in FIG-- URE 1 a magnetrondevice embodying a form of my invention. The device of FIGURE 1 includesan envelope generally designated 1 and constituted of a stacked assemblyof alternately arranged and suitably sealed metal and ceramic memberswherein some of the metal members serve as electrical terminals ofthedevice and the ceramic members serve as insulative spacers betweenthe metal members. The metal members which serve as electrical terminalsinclude a pair of annular anode terminals 2 and 3, separated by aceramic cylinder-.4. The metal members further include a frusto-conicalcontrol electrode 5 which includes a flanged or annular portion 6separated 13 comprises the cold or non-emissive cathode of the deviceand the dimensions and disposition of the cylindrical active surfaceportion thereof relative to other electrode elements in the device,aswell as the shape and disposition of the surface '12, play importantparts in my invention and will be described in greater detailhereinafter. The outer surface of the member comprises an electricalterminal for the cold cathode.

The magnetron device illustrated is of the interdigital type and thecold cathode 13 extends partially in an anode assembly or circuit whichincludes two sets of axially extending elongated anode segmentsalternately arranged in a cylindrical array supported concentricallywithin the envelope 1 by the anode terminals 2 and 3. Alternate segments14 and 15 are connected to different ones of the annular anodes 2 and 3,respectively, thus to provide two groups of anode segments alternatelyarranged in the array with each group connected to one of the terminals2 or 3. The segments 14 and 15 are slightly separated to provide axiallyextending interaction gaps. As is well understood in the art, it is theinteraction between the high frequency field across these gaps and arotating and bunched space charge that effects the desired energytransfer from the space charge to the oscillatory circuit of the anode.As is also Well understood in the art, the electron rotation resultsfrom the provision of an axial magnetic field through the device. Such afield is usually provided by disposing the magnetron between the opposedpoles P of a magnet in the manner illustrated in FIGURE 1.

The electrons constituting the rotating beam are emitted from a hotcathode or emitter 16 disposed in a region of the envelopelongitudinally displaced from the array of anode segments, and theentrance of the electrons into the region of the interaction gaps isunder control of the control electrode 5. In the embodiment illustrated,the emitter 16 is supported by a ceramic or disk 17 which serves also toclose the other end of the envelope 1. The emitter 16 can be of thedirectly-heated filamentary type illustrated and formed, for example, ofthoriated tungsten Wire. Additionally, it can be bifilar and contrawoundor, in other words, can comprise a double helix structure wherein thehelices are mutually oppositely wound. Both ends or leads 18 of thefilament are disposed at one end thereof and, as shown, the hot cathodecan be mounted and solely supported in the envelope by means of theleads 18. The leads 18 include portions which extend radiallysubstantially from the axis of the cathode and are suitably sealed inapertures 20 parallelly extending in spaced relation through the ceramicdisk 17. Connected to the outer extremities of the leads 18 is a pair ofcontact buttons 21 which can be suitably brazed to the outer surface ofthe ceramic disk 17. The buttons 21 are effective for completing anelectrical circuit through the countrawound filamentary emitter, therebyto render same emissive and provide a cloud of electrons about thefilament in the lower region of the device.

Also brazed to the outer surface of the ceramic disk 17 is a controlelectrode contact'button 22. The button 22 can be brazed to the disk 17in the same manner as the buttons 20. Additionally, the button 22 issuitably electrically connected to a tantalum or tungsten lead 23 whichextends through and is sealed ina suitable aperture 24 extending throughthe disk 17. The upper end of the aperture 24 opens directly beneath theflange 6 of the control electrode 5 and the upper or inner end of thelead 23 is suitably electrically connected to the flange 6, whereby thebutton 22 is adapted for serving as the contact for making an electricalconnection to the control electrode 5.

The control electrode 5 includes, in addition to the flange 6, a tubularportion 25 extending from the flange 6 thereof toward the interactionspace of the device. The tubular portion 25 is frusto-conical in shapeand includes an inner surface which is spaced progressively closer tothe filamentary cathode 16 in an axial direction toward the anodeassembly. In operation, the control electrode 5 is maintained at apositive potential with respect to the emitter 16 so that an axialcomponent of velocity toward the interaction space is imparted to theelectrons emanating from the emitter. As illustrated, the frusto-conicalportion of the control electrode terminates in closely spaced relationto the anode. This spacing is preferably about 10 mils. Additionally,and as also illustrated, the control electrode is provided with aninternal cylindrical surface 26 adjacent the anode. The cylindricalsurface 26 is preferably about 20 mils in length and has a diameter atleast equal to and optionally slightly smaller than that of thecylindrical surface defined by the inner surfaces of the anode segments.Additionally, the inner edge 27 of the surface 26 corresponds generallyin axial position to the upper end of the emitter. This arrangementminimizes back-heating of the cathode and undesirable electronimpingement and collection on the lower ends of the anode array, or, inother words, relatively disposes the control electrode, emitter andlower ends of the anode segments such that the control electrode shieldsthe lower ends of the anode segments and directs substantially allelectrons into the cylindrical space defined by the anode segments.

The control electrode 5 and the particular spacing thereof from theanode contribute to the effectiveness of the control electrode ininjecting a substantial number of electrons into the annular interactionregion between the cold cathode 13 and the anode segments 14 and 15.This injection is particularly desirable in voltage-tunable magnetrondevices since, under the conditions as existing during operation, thehigh frequency fields between adjacent anode segments are relativelyweak in comparison with those existing in tank-tuned operation. In thespecific embodiment of the device illustrated in FIG- URE 1 theinjection is believed to be facilitated by the frusto-conicalconfiguration of the control electrode. In this embodiment the wall ofthe control electrode extends at an angle of approximately 30 withrespect to the axis of the conical portion and the cylindrical surface26 of the control electrode, as pointed out above, has an axial lengthof approximately 20 mils.

The above-mentioned interaction region is defined by the cylindricalactive surface of the cold cathode 13 and the anode segments 14 and 15and in the illustrated embodiment of my invention the cold cathode iscylindrical throughout its full length and extends in the anode arrayonly approximately two-thirds of the axial length of the latter. Thisdisposes the specific interaction region, or the region in which thecylindrical active surface of the cold cathode 13 directly opposes thevertical surfaces of the anode segments 14 and 15, somewhat remote fromthe emitter and control electrode and leaves a substantial hollow spacegenerally designated 30 between the inner end of the cold cathode andthe inner ends of the control electrode and emitter. I have found thisarrangement highly effective and advantageous from the standpoints ofincreased operating efficiency, increased power output and increasedstability of performance. The manner in which these increased operatingcharacteristics are obtained by the disclosed electrode arrangement willbe better understood by reference to the schematic illustration of myimproved electrode arrangement found in FIGURE 2.

In normal operation of my device, electric fields are establishedbetween the control electrode and emitter, between the anode andemitter, and between the anode and cold cathode of the device. Inestablished electric fields between the several electrodes, and as seenin FIG- URE 2, there are substantially curved field lines shown in dashlines designated 31 and extending between the edge of the controlelectrode 5 and the emitter 16 and between the anode segments 14 and 15and the emitter 16. These result in curved equi-potential surfacesgenerally of the hour-glass like configurations illustrated by solidlines 32 in FIGURE 2 and substantial axial and radially inwardlyextending field components tending to act on electrons emanating fromthe emitter for directing them J axially toward the cold cathode andinwardly toward the center of the hollow space 31 It will also be seenfrom FIGURE 2, that substantially curved field lines exist between theanode segments 14 and 15 and the transverse end surface 13a of the coldcathode 13. These result in substantial axial and radially outwardlyextending components tending to direct the electrons axially andsomewhat radially outwardly into the interaction region between anddefined by the lateral surface of the cold cathode 13 and the anodesegments 14 and 15.

It will be understood that the static axial magnetic field providedbetween the poles P additionally affects the movement of the electronsand tends to rotaate them about the axis of the device as they emanatefrom the emitter, while in the space 30 and subsequently in theinteraction region for effecting transfer of energy to the radiofrequency field. Additionally, when electrons start rotating at a smallradius they are thereby adapted for surrendering greater energy to aradio frequency field. In my disclosed improved electrode arrangementthe hollow space 3% enables the electrons emanating from the cathode toapproach the axis of the device before being rotated outwardly towardthe interaction region and the axial and radially inwardly extendingfield components in the lower portion of the space 3% are effective forquickly directing electrons from the emitter toward the central regionof the space 30 wherein they are adapted for being rotated at a smallradius relative to the radius of the interaction region. Thus, myelectrode arrangement is effective for adapting the electrons tosurrender greater energy to the radio frequency field when the axial andradially outwardly extending field components in the upper portion ofthe space 30 subsequently direct the electrons into the interactionregion between the cylindrical surface of the cold cathode 13 and theanode segments 14 and 15.

Additionally, the manner in which my improved electrode arrangementdirects the electrons into the interaction region also has the desirableeffect of minimizing the collection of electrons on the transverse endsurface 13a of the cold cathode and, thus, increasing the total amountof electrons entering the interaction region wherein they can beeffective for transferring energy to the radio frequency field, therebyto increase the power output.

My improved electrode arrangement and the electric field configurationestablished thereby are also effective for rotating the electronstransferred from the emitter into the interaction region incircumferential direction at an average velocity in a manner which aidsin the interaction. The average circumferential velocity which isdetermined by the combined effect of the radial electric fieldcomponents and the axial magnetic components is gradually increased inthe injection area or in the space 36 so that there results a smoothtransition from the angular velocity of the electrons emanating from thecontrol elect-rode to the velocity in the interaction region. In priorart devices the interaction region defined by the active surface of thecold cathode and the anode extends to the immediate vicinity of theemitter and control electrode and the cold cathode is sometimescylindrical throughout its length and is physically connected to theemitter with the result that the change in velocity of electronsrotating in the injection area to the velocity in the interaction regionbetween the cold cathode and anode is substantially sudden. In myimproved electrode arrangement the space Sit and the field distributiontherein affords a smooth transition in velocity of electrons rotating inthe injection area to the velocity of electrons rotating in theinteraction region for thus affording an increased stability ofperformance not obtainable with prior art structures. i

It will be understood that while I have found the extension of thecylindrical active surface of the cold cathode 13 into the anodeassembly only approximately twothirds of the axial length of the latterproduces an optimum arrangement of electrodes for increasing'efiiciency,power output and stability of performance, slight deviations can be madefrom this relationship'without deviating from my invention. However, anysubstantial deviation, such as an extension of the active surface of thecold cathode into the anode to a point immediately adjacent theinnermost or bottom edges of the anode segments, will result inoperation which is different in kind in that it will not afford theunexpected increases in.

operating efficiency, power output and stability of performanceobtainable when the active surface of the cold cathode extends into theanode only approximately twothirds the length of the anode segments inaccordance with my present teaching. 1

Increased power output is obtainable with my device efiect on theelectrons in the upper portion of the inter-' action region which tendsto reduce the amount of energy transferred from electrons rotating inthe upper portion of the interaction region to the radio frequencyfield. I have also found that this end effect can be relieved and theeffective length of the interaction region can be virtually increased byproviding the tapered surface 12 in place of the previously employedcylindrical boss. It is believed that, unlike the cylindrical end bossesfound in prior art devices, the tapered surface 12 results in a fielddistribution between the upper ends of the cold cathode 13 and the anodesegments 14 and 15 which enables a more uniform reaction betweenelectrons and the radio frequency field throughout the length of thereactive region. capabilities for the device over a substantially widefrequency range. It is also believed that the tapered surface 12 reducescapacity between the anode and cold cathode which is considereddesirable because in operation these elements are generally connected toa modulating source and the reduced capacity reduces the requiredmodulating power, especially at higher operating frequencies.

The increased power capabilities of magnetrons embodying my inventionwill perhaps be better appreciated by a consideration of the family ofcurves illustrated in FIGURE 3 and showing the different high'frequencypower outputs obtained with voltage tunable magnetrons incorporating myinvention wherein the interaction region extends only approximatelytwo-thirds the length of the anode and a frusto-conical surface isprovided on the upper .end of the cold cathode and a prior art devicewherein the cold cathode extends for substantially the full length ofthe anode and a cylindrical boss is employed in the upper end of thecold cathode.

In FIGURE 3 the solid line curve represents the power output of a deviceincmporatingmy improved electrode arrangement and the dash line curverepresents that of the .prior device. Both devices were operated in anaxial magnetic field between the poles P and adjusted to a value of 2400gauss.

The filament current was adjusted to approximately 3.0 amperes DC. atabout 3.4 volts, the control electrode potential at approximately plus450400 volts, and the from about 2150 megacycles to about 390 0megacyclesj In this range of frequency and as illustrated in FIGURE 3,my improved device provided an averagepower output of approximately 4.5watts, where the modulation voltage to sweep over the band offrequencies was a sinusoidal source, whereas the prior art deviceattained an'average power output of approximately only 1.7 watts.Thisty'pe of performance has been repeatable with different tubes I havefound that This, it is believed, results in greater power.

with my improved structure always affording increased power outputs ofat least more than 2 to 1 compared with the prior art device.Additionally, with some tubes incorporating my improved structure I haveobtained up to 10 watts average power output. Also, I have attainedthese substantially higher average power outputs with increasedoperating efliciency and increased stability of performance.

It will be understood from the foregoing and reference to FIGURE 4 thatmy invention is not limited to structure wherein the anode segments arearrayed cylindrically. Alternatively, the anode can comprise a pluralityof sets of interdigital anode segments supported in mutually spacedside-by-side relation in an elongated array in the manner shown inFIGURE 4. The structure of FEGURE 4 includes a first set of elongatedanode segments 35 suitably conductively mounted on a conductive supportbar 36. A second set of such segments designated 37 is mounted similarlyon another conductive support bar 38. As shown, these sets of segmentsare interdigitally arranged and mutually spaced and insulated.

Cooperating with the anode is a non-emissive electrode or cold cathode39. The cold cathode 39 is elongated and extends in spaced relation tothe anode array. The underside of the cold cathode 39, as viewed inFIGURE 4, constitutes the active surface thereof for cooperating withthe anode segments to define an interaction region. The width of thecold cathode 39 is such that the active surface thereof extends onlyapproximately two-thirds the length of the segments 35 and 37.Additionally, the

cold cathode 39 includes a tapered surface 49 outwardly of theinteraction gap and inclined toward the plane of the anode segments.This surface serves the same purpose as the frusto-conical surface 12 inthe device illustrated in FIGURE 1.

Disposed in spaced relation to the side of the anode opposite thesurface 40 on the cold cathode is an emitter 41. The emitter 41 isspaced from the corresponding ends of the anode segments and iselongated to extend the length of the array of segments. Cooperatingwith the emitter 41 is an elongated control electrode 42. The controlelectrode 42 can include tapered surfaces for facilitating andcontrolling direction or injection of electrons from the regionsurrounding the emitter toward the interaction region between the coldcathode and anode.

As seen in FIGURE 4, the just-described structure provides anarrangement of electrodes in which the interaction region is somewhatremote from the emitter while a portion of the anode extends to theimmediate vicinity of the emitter. Additionally, the device is adaptedfor operating in a magnetic field extending parallel to the anodesegments. This field can be supplied, for example, by magnet polesdesignated P and shown'in dash lines. Thus, the device of FIGURE 4 willbe understood from the foregoing to be similar in structure andoperation to the device shown in FIGURES 1 and 2. For ease ofunderstanding the structure of FIGURE 4 will be understood from theforegoing to be similar in structure and operation to the device shownin FIGURES 1 and 2. For ease of understanding, the structure of FIGURE 4might be reasonably viewed as a plan development of the cylindricalstructure of FIGURE 1.

However, it will be noted that the structure of FIG- URE 4 enables theemployment of an elongated emitter which increases substantially theamount of electrons which can be introduced into the interaction region.Thus, the structure of FIGURE 4 has substantially greater powercapabilities due to the increased emission. This, together with theincreased power output resulting from my disclosed arrangement ofelectrodes, results in still greater power capabilities.

In both of the illustrated embodiments I have shown cold cathodes havingactive surfaces extending the full lengths thereof and which cathodesdetermine the dispositions and lengths of the interaction regions by thedimensions of the cathodes relative to the lengths of the anodesegments. However, it is to be understood that portions of the cathodescan, if desired, extend toward the emitter beyond the interaction regionwithout departing from or losing the benefits of my invention. Thus, forexample, the inner end of the cathode post 13, in FIGURE 1 can betapered or conical in the manner shown at 13b in FIGURE 1A. Thecylindrical active surface of the cold cathode in this form, and thusthe interaction region, remains substantially the same length as thecold cathode in FIGURE 1 and the tapered end 13b extends about thelength of the anode segments into the space designated 30. This type ofarrangement is still effective for causing rapid introduction ofelectrons into the interaction region and for allowing the electrons tocommence rotating at a small radius for increasing the energy transferand to experience a smooth transition in the average velocity ofelectrons introduced into the interaction region. With this tapered formof cold cathode post I have been able to obtain consistently averagepower outputs up to 9 watts. It will be further understood from theforegoing that the end of the cold cathode 39 in FIGURE 4 can also, ifdesired, be tapered or otherwise shaped and in a manner such as not tointerfere with the operation of the device to afford substantiallyincreased power output and other improved operating characteristics.

While I have shown and described specific embodiments of my invention 1do not desire my invention to be limited to the particular forms shownand described, and I intend by the appended claims to cover allmodifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A cross-field electric discharge device comprising an interdigitalanode circuit including a plurality of elongated segments supported inmutually spaced, side-by-side relation, an emissive cathode whollydisposed in longitudinally spaced relation at the ends of said segmentsat one side of said anode, a non-emissive cathode including an activesurface extending only partially the lengths of said segments andcooperating with said segments to define an interaction regiontherebetween, said interaction region being shorter than said anodesegments and being spaced a substantially greater amount from saidemissive cathode than said ends of said segments, and means fordirecting electrons from said emissive cathode toward said interactionregion.

2. A cross-field device comprising an interdigital anode circuitincluding a plurality of segments supported in mutually spaced relationand defining a cylindrical opening, an electron emissive cathode whollydisposed axially outwardly of one end of said opening, a non-emissivecathode axially spaced and electrically separated from said emissivecathode extending in said opening from the other end thereof andincluding a lateral active surface extending only partially the lengthsof said segments, said active surface of said non-emissive cathode andsaid segments thus defining an annular interaction region therebetweenin which the active surface of said non-emissive cathode is spaced asubstantially greater amount from said emissive cathode than said anode,and means for directing electrons from said emissive cathode axiallyinto said one end of said opening in said anode circuit toward saidinteraction region.

3. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, an electron emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendingonly partially in said opening from the other end thereof, whereby saidnon-emissive electrode and said segments define an annular interactionregion therebetween and the partial extension of said non-emissiveelectrode in said opening affords a hollow space in said opening axiallyinterposed between said interaction region and said emissive electrode,and means for directing electrons from said emissive electrode axiallyinto said one end of said opening in said anode circuit toward saidinteraction region and inwardly toward the center of said hollow space,thereby to adapt said electrons for rotating in said hollow space at asmaller radius relative to the radius of said interaction region andbefore entering said interaction region.

4. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, an electron emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendingin said opening from the other end thereof and including an activesurface extending parallel to and only partially the lengths of saidsegments, said active surface of said non-emissive electrode and saidsegments defining an annular interaction region therebetween in whichthe active surface of said non-emissive electrode is longitudinallyspaced from said emissive electrode a substantially greater amount thansaid anode, and a coaxial electrode about said emissive electrode, saidelectrodes cooperating to establish an electric field eifective fordirecting electrons first axially and radially inwardly toward thelongitudinal axis of said opening and then axially and radiallyoutwardly into said interaction region.

5. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, an electron emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendinginto said opening approximately two-thirds the axial length of saidsegments, whereby said non-emissive electrode and said segments definean annular interaction region therebetween and the partial extension ofsaid non-emissive electrode in said opening aifords a hollow space insaid opening axially interposed between said interaction region and saidemissive electrode, and means directing electrons from said emissiveelectrode axially toward said interaction region and inwardly toward thecenter of said hollow space, thereby to adapt said electrons forrotation in said hollow space at a smaller radius relative to the radiusof said interaction region and before entering said interaction region.

6. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, an electron emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendinginto said opening approximately two-thirds the axial length of saidsegments, whereby said non-emissive electrode and said segments definean annular interaction region therebetween and the partial extension ofsaid non-emissive electrode in said opening affords a hollow space insaid opening axially interposed between said interaction region and saidemissive electrode, and a coaxial control electrode about the end ofsaid emissive electrode adjacent said opening and having an edge axiallyinterposed between said anode and said end of said emissive electrode,said control electrode and said emissive electrode cooperating toprovide axial and radially inwardly directed field components fordirecting electrons from said emitter axially toward said interactionregion and inwardly toward the center of said hollow space, thereby toadapt said electrons for rotation at a smaller radius than the radius ofsaid interaction region before entering said interaction region, andsaid anode, emissive electrode and non-emissive elec trode cooperatingto provide axially and radially outwardly directed field components forfacilitating movement of rotating electrons into said interaction regionfrom said hollow space.

7. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, a coaxial emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendingonly partially in said opening from the other end thereof, saidnon-emissive electrode having an annular tapered surface outside saidother end of said anode opening and increasing in diameter away fromsaid opening, said non-emissive electrode and said segments defining anannular interaction region therebetween and the partial extension ofsaid nonemissive electrode in said opening affording a hollow space insaid opening axially interposed between said interaction region and saidemissive electrode, and means for directing electrons from said emissiveelectrode axials ly into said one end of said opening in said anodecircuit toward said interaction region and inwardly toward the center ofsaid hollow space, thereby to adapt said electrons for rotating in saidhollow space at a smaller radius relative to the radius of saidinteraction region before entering said interaction region, and saidtapered surface on said non-emissive electrode being effective forcooperating with said segments for virtually increasing the effectivelength of said interaction region.

.8. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, a coaxial emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendingin said open ing approximately two-thirds the axial length of saidsegments, said non-emissive electrode having a frusto-conical surfaceoutside said other end of said anode opening and increasing in diameteraway from said opening, said nonemissive electrode and said segmentsdefining an annular interaction region therebetween and the two-thirdsextension of said non-emissive electrode in said opening affording ahollow space in said opening axially interposed between said interactionregion and said emissive electrode, and a coaxial frustoconical controlelectrode surrounding said emissive electrode and having the smalleredge thereof axially interposed between said anode and said emissiveelectrode, said control electrode and said emissive electrodecooperating to provide axial and radially inwardly directed fieldcomponents for directing electrons from said emissive electrode axiallytoward said interaction region and inwardly toward the center of saidhollow space, thereby to adapt said electrons for rotating at a smallerradius-than the. radius of said interaction region before entering saidinteraction region, said anode, emissive electrode and non-emissiveelectrode cooperating to provide axially and radially outwardly directedfield components for facilitating movement of rotating electrons intosaid interaction region from said hollow space, and

said frusto-conical surface on said non-emissive electrode cooperatingwith said segments for virtually increasing the effective length of saidinteraction region.

9. A cross-field electric discharge device comprising an interdigitalanode circuit including a plurality of segments supported in mutuallyspaced side-by-side relation in an elongated planar array, an elongatedemissive cathode disposed along one edge of said planar array in spacedrelation to the ends of said segments, an elongated nonemissive cathodeelectrically separated from said emissive cathode extending in spacedco-extensive relation to said array and having an active surface forcooperating with said segments to define a planar interaction regiontherebetween, said interaction region being shorter in width than thelength of said segments and being spaced a substantially greater amountfrom said emissive cathode than said anode, and means for directingelectrons from said emissive cathode toward said interaction region.

10. A cross-field electric discharge device comprising an anodeincluding a plurality of segments supported in mutually spacedside-by-side relation in an elongated array, an elongated emitterdisposed along one edge of said array in spaced relation at the ends ofsaid segments, an

elongated non-emissive electrode extending in spaced coextensiverelation to said array and cooperating therewith to provide aninteraction region, said non-emissive electrode extending toward saidemitter only approximately two-thirds the length of said segments,whereby the interaction region defined by said non-emissive electrodeand cathode is remote from said emitter relative to said one edge ofsaid array, and means for directing electrons from said emitter towardsaid interaction region.

11. A cross-fieid device according to claim 9, wherein a controlelectrode cooperates with said emissive cathode and other electrodes forestablishing an electric field effective for directing electrons towardsaid interaction region.

12. A cross-field device according to claim 9, wherein said non-emissivecathode has a surface thereon inclined toward said array of segments onthe side of said anode opposite said emissive cathode for cooperatingwith said segments to increase virtually the effective length of saidinteraction region.

13. A cross-field electric discharge device comprising an anodeincluding a plurality of elongated segments supported in mutuallyspaced, side-by-side relation, an emitter disposed in longitudinallyspaced relation at the ends of said segments at one side of said anode,a nonemissive electrode extending in laterally spaced relation to saidanode and having an active surface extending parallel to and cooperatingwith said segments to define an interaction region therebetween, saidinteraction region being spaced a substantially greater amount from saidemitter than said ends of said segments, and said nonemissive electrodeincluding a tapered end portion extending toward said emitter.

14. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, an electron emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode includinga cylindrical active surface extending only partially in said openingfrom the other end thereof and defining with said segments an annularinteraction region extending only partially the length of said segments,and said non-emissive electrode further including a tapered endextending toward said emissive electrode and longitudinally spaced andelectrically separated therefrom by a void.

15. A cross-field electric discharge device comprising an envelope, saidenvelope supporting an anode including a plurality of elongated segmentsmounted in mutually spaced, side-by-side relation in said envelope, aninsulative member closing one end of said envelope, a filamentaryemitter in said envelope having both ends thereof sealed through saidinsulative member and solely supported thereby, said emitter beinglocated in longitudinally spaced relation to the ends of said segmentsat one side of said anode, a non-emissive electrode extending in saidenvelope in laterally spaced relation to said anode and cooperating withsaid segments to define an interaction region therebetween extendingonly partially the length of said anode segments and being spaced asubstantially greater amount from said emitter than said ends of saidsegments, and means for directing electrons from said emitter towardsaid interaction region.

16. A cross-field electric discharge device comprising an envelope, saidenvelope supporting an anode including a plurality of elongated segmentsmounted in mutually spaced, side-by-side relation in said envelope, aninsulative member closing one end of said envelope, a filamentaryemitter in said envelope having both ends thereof sealed through saidinsulative member and solely supported thereby, said emitter beinglocated in longitudinally spaced relation to the ends of said segmentsat one side of said anode, a non-emissive electrode extending in saidenvelope in laterally spaced relation to said anode and cooperating withsaid segments to define an interaction region therebetween extendingonly partially the length of said anode segments and being spaced asubstantially greater amount from said emitter than said ends of saidsegments, and said non-emissive electrode having a frustoconical surfacethereof disposed outwardly of said interaction region at the other sideof said anode and inclined toward said anode segments.

17. A magnetron comprising an anode circuit including a plurality ofsegments supported in mutually spaced relation and defining acylindrical opening, an electron emissive electrode disposed axiallyoutwardly of one end of said opening, a non-emissive electrode extendingonly partially in said opening from the other end thereof, whereby saidnon-emissive electrode and said segments define an annular interactionregion therebetween and the partial extension of said non-emissiveelectrode in said opening affords a void in said opening axiallyinterposed between said interaction region and said emissive electrode,and means for drecting electrons from said emissive electrode axiallyinto said one end of said opening in said anode circuit toward saidinteraction region.

References Cited in the tile of this patent UNITED STATES PATENTS 2409,038 Hansell Oct. 8, 1946 2,493,423 Spooner Jan. 3, 1950 2,509,419Brown May 30, 1950 2,585,741 Clogston Feb. 12, 1952 2,810,096 PetersOct. 15, 1957 en T

